Pick out an image that you want to use, go to the store and buy a sheet of cardstock for each color. Also, buy the background color and a piece of foamcore if you want to mount it on a solid background and get some doublesided foam sticky pad thingies. They are probably 1/8th inch thick and the ones I got came in a roll.

Assembling is pretty easy. Just think about trying to hide the mechanics of the pieces below the top ones. Just take your time and do a couple quick sketches on printer paper of the layout before you cut and paste.

Let me know if you decide to go for it and I'll give you a couple more pointers!